Method and system for operating a satellite communication system with regional redundant sites and a central site

ABSTRACT

A method and system for operating a satellite communication system with regional redundant sites and a central site includes a satellite and a regional site uplinking regional uplink signals to the satellite and condition signals to a terrestrial communication link. The satellite generates regional downlink signals from the regional uplink signal. A central site receives the regional downlink signals from the satellite and terrestrially receives the condition signals and generates control signals for the regional site through the terrestrial communication link.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is related to Utility application Ser. Nos. 11/529,932,11/529,915, 11/529,949, 11/529,950, 11/529,918, and 11/540,037, allfiled simultaneously herewith on Sep. 29, 2006. The disclosures of theabove applications are incorporated by reference herein.

TECHNICAL FIELD

The present disclosure relates generally to satellite communicationsystems, and more particularly to a method and system for operating asatellite communication system with regional redundant sites and acentral site.

BACKGROUND

The statements in this section merely provide background informationrelated to the present disclosure and may not constitute prior art.

Satellite broadcasting of television signals has increased inpopularity. Satellite television providers continually offer more andunique services to their subscribers to enhance the viewing experience.Providing reliability in a satellite broadcasting system is therefore animportant goal of satellite broadcast providers.

Using a redundant site for uplinking is known. However, reliability insuch sites may still be compromised and, thus, the service may beperceived as less than reliable.

SUMMARY

In one aspect of the disclosure, a system includes a satellite, aregional site uplinking regional uplink signals to the satellite andcondition signals to a terrestrial communication link. The satellitegenerates regional downlink signals from the regional uplink signal. Acentral site receives the regional downlink signals from the satelliteand terrestrially receives the condition signals and generates controlsignals for the regional site through the terrestrial communicationlink.

In a further aspect of the disclosure, a method includes uplinkingregional uplink signals to a satellite, uplink condition signals to aterrestrial communication link, generating regional downlink signals atthe satellite from the regional uplink signal, receiving the regionaldownlink signals at a central site, receiving the condition signals at acentral site and communicating and generating control signals for theregional site through the terrestrial communication link at the centralsite.

One advantage of the disclosure is that by distributing the uplinkingsignals with both primary and diverse sites at various regions and at acentral site, more reliable satellite signals may be received by thevarious users.

Further areas of applicability will become apparent from the descriptionprovided herein. It should be understood that the description andspecific examples are intended for purposes of illustration only and arenot intended to limit the scope of the present disclosure.

DRAWINGS

The drawings described herein are for illustration purposes only and arenot intended to limit the scope of the present disclosure in any way.

FIG. 1 is an overall system view of a satellite communication system inthe continental United States.

FIG. 2 is a system view at the regional level of a satellite system.

FIGS. 3A, 3B and 3C are block diagrammatic views of the systemsillustrated in FIGS. 1 and 2.

FIG. 4 is a flowchart illustrating a method of operating the systemillustrated in FIG. 3.

FIGS. 5A and 5B are schematic views of a primary or diverse siteillustrated in FIGS. 3A-C.

FIG. 6 is a cutaway view of an antenna according to the presentdisclosure.

FIG. 7 is a flowchart illustrating switching logic for a primary anddiverse site.

FIGS. 8A and 8B are flowcharts for determining a primary site equipmentstatus and a diverse site equipment status, respectively.

FIGS. 9A and 9B are flowcharts of an emergency primary to diverse ordiverse to primary emergency switchover, respectively.

FIGS. 10A and 10B are flowcharts of a diverse site initialization and aprimary site initialization, respectively.

FIGS. 11A and 11B are flowcharts illustrating a radiate/terminatefunction for a diverse switch and a primary switch, respectively.

FIGS. 12A and 12B are flowcharts of a primary site second trigger pointand a diverse site trigger point, respectively.

FIG. 13 is a flowchart of a primary clear sky normalized diverse sitemethod of FIG. 12A.

FIGS. 14A and 14B are flowcharts of a primary to diverse site switch ordiverse to primary site switch, respectively.

FIG. 15 is a flowchart of a primary site clear sky time durationfunction.

FIG. 16 is a flowchart of a switch to normal path function.

FIG. 17 illustrates a summary of a switchover between a primary site anda secondary site.

FIG. 18 is a high level view of an integrated receiver decoder having anerror conceal module.

FIGS. 19A and 19B are timing charts illustrating the primary sitesignal, secondary site signal and a gap.

FIG. 19B is a timing chart showing the primary site signal and secondarysite signal after error correction.

FIG. 20 is a flowchart illustrating a method for controlling uplinkpower.

FIG. 21 is a plot of uplink power versus fade.

FIG. 22 is a flowchart of a method of receiving a beacon signalaccording to the present disclosure.

DETAILED DESCRIPTION

The following description is merely exemplary in nature and is notintended to limit the present disclosure, application, or uses. Itshould be understood that throughout the drawings, correspondingreference numerals indicate like or corresponding parts and features.

The present disclosure is described with respect to a satellitetelevision system. However, the present disclosure may have various usesincluding satellite transmission and data transmission and reception forhome or business uses.

Referring now to FIG. 1, a communication system 10 includes a satellite12. The communication system 10 includes a central facility 14 and aplurality of regional facilities 16A, 16B, 16C, 16D, 16E and 16F.Although only one satellite is shown, more than one is possible. Theregional facilities 16A-16F may be located at various locationsthroughout a landmass 18 such as the continental United States,including more or less than those illustrated. The regional facilities16A-16F uplink various uplink signals 17 to satellite 12. The satellitesdownlink downlink signals 19 to various users 20 that may be located indifferent areas of the landmass 18. The users 20 may be mobile or fixedusers. The uplink signals 17 may be digital signals such as digitaltelevision signals or digital data signals. The digital televisionsignals may be high definition television signals. Uplinking may beperformed at various frequencies including Ka band. The presentdisclosure, however, is not limited to Ka band. However, Ka band is asuitable frequency example used throughout this disclosure. The centralfacility 14 may also receive downlink signals 19 corresponding to theuplink signals 17 from the various regional facilities and from itselffor monitoring purposes. The central facility 14 may monitor the qualityof all the signals broadcast from the system 10.

The central facility 14 may also be coupled to the regional facilitiesthrough a network such as a computer network having associatedcommunication lines 24A-24F. Each communication line 24A-F is associatedwith a respective regional site 16. Communication lines 24A-24F areterrestrial-based lines. As will be further described below, all of thefunctions performed at the regional facilities may be controlledcentrally at the central facility 14 as long as the associatedcommunication line 24A-F is not interrupted. When a communication line24A-F is interrupted, each regional site 16A-F may operate autonomouslyso that uplink signals may continually be provided to the satellite 12.As will be described below, the central facility 14 may include graphicuser interfaces that are identical to those of the regional site 16 sothat control and monitoring can take place at the various regionalfacilities. Each of the regional and central facilities includes atransmitting and receiving antenna which is not shown for simplicity inFIG. 1.

Referring now to FIG. 2, the regional facilities 16A-16F are illustratedcollectively as reference numeral 16. The regional site 16 may actuallycomprise two facilities that include a primary site 40 and a diversesite 42. As will be described below, the central site 14 may alsoinclude a primary site and diverse site as is set forth herein. Theprimary site 40 and diverse site 42 of both the central and regionalsites are preferably separated by at least 25 miles, or, morepreferably, at least 40 miles. In one constructed embodiment, 50 mileswas used. The primary site 40 includes a first antenna 44 fortransmitting and receiving signals to and from satellite 12. Diversesite 42 also includes an antenna 46 for transmitting and receivingsignals from satellite 12.

Primary site 40 and diverse site 42 may also receive signals from GPSsatellites 50. GPS satellites 50 generate signals corresponding to thelocation and a precision timed signal that may be provided to theprimary site 40 through an antenna 52 and to the diverse site 42 throughan antenna 54. It should be noted that redundant GPS antennas (52A,B)for each site may be provided as illustrated in FIG. 5. In someconfigurations, antennas 44 and 46 may also be used to receive GPSsignals.

A precision time source 56 may also be coupled to the primary site 40and to the diverse site 42 for providing a precision time source. Theprecision time source 56 may include various sources such as coupling toa central atomic clock.

The primary site 40 and the diverse site 42 may be coupled through acommunication line 60. Communication line 60 may be a dedicatedcommunication line. The primary site 40 and the diverse site 42 maycommunicate over the communication line using a video over internetprotocol (IP).

Various signal sources 64 such as an optical fiber line or copper linemay provide incoming signals 66 from the primary site 40 to the diversesite 42. Incoming signal 66, as mentioned above, may be televisionsignals. The incoming signals 66 such as the television signal may berouted from the primary site 40 through the communication line 60 to thediverse site 42 in the event of a switchover whether the switchover ismanual or a weather-related automatic switchover. A manual switchover,for example, may be used during a maintenance condition.

Users 20 receive downlink signals 70 corresponding to the televisionsignals. Users 20 may include home-based systems or business-basedsystems, both mobile and fixed. As illustrated, a user 20 has areceiving antenna 72 coupled to an integrated receiver decoder 74 thatprocesses the signals and generates audio and video signalscorresponding to the received downlink signal 70 for display on thetelevision or monitor 76. It should also be noted that satellite radiosystems may also be used in place of an IRD and TV for use of thesatellite signals.

Referring now to FIGS. 3A, 3B and 3C, block diagrammatic views of thecontrol system of the communication system of the present disclosure areillustrated. In FIG. 3, the central site 14 includes the primary site14A and the diverse site 14B. A monitoring module 90 is illustratedlocated at the primary central site 14A. Those skilled in the art willrecognize that the monitoring module 90 may be located in variouslocations including separately from the primary site.

Monitor module 90 may include a system server 91 and displays 92, 94 and96 that display graphical user interfaces for status and control ofvarious functions that will be further described below. The serversystem 91 is a controller that may control the overall system function.The server may generate control signals that act as a switch. Theswitches or switch functions may be performed in software alone or inconjunction with various relays or other suitable hardware thatcorresponds to the particular equipment controlled. The switch ofvarious system components is performed in response to various monitoredconditions. The displays 92, 94 and 96 may be formed on multiple monitorscreens or on different monitor screens. The status and controlmonitoring may be able to monitor and control the elements in the RFchain and various other conditions associated with satellitetransmission and reception.

The server 91, the displays 92, 94 and 96 may be coupled to a router100. The router 100 may receive information from the various primary anddiverse sites for display on the graphical user interfaces so that anoperator may easily control various functions at the diverse sites. Therouter 100 may, therefore, act as a switch or a number of switches forrouting various input and output signals.

The primary site and the diverse site for each of the central site andthe remote sites may be configured identically or nearly identically.Each of the sites includes a router 150 that has various elementscoupled thereto. It should be noted that various elements may be coupledtwice to provide redundancy in the system. For example, a server 152 iscoupled to router 150. A second server 154 is also coupled to router 150to provide redundancy to the first server 152. The servers 152, 154 mayact as a controller to switch on and off various components of thesystem in response to monitored condition signals. Block upconverters156 and block downconverters 158, as well as block upconverters 160 andblock downconverters 162, are coupled to the router 150. A globalpositioning switch 164 and a global positioning system receiver 166 arealso coupled to the router. A second global positioning receiver 168 iscoupled to router 150. An antenna control unit 170 and a second antennacontrol unit 172 are also coupled to the router 150. The router 150 mayalso receive information from various elements in the receive andtransmit chain. The router 150 may route these receive signals to thevarious servers 152 and 154 for processing and control purposes. Therouter 150, for example, may receive information through a first serialport 180 and a second serial port 182. The serial ports may be coupledto high-power amplifiers 184, 186, tracking receive interface 188, 190,variable power combined amplifiers 192, 194 and spectrum analyzer 196,198.

The router 150 may also be discretely wired to various input sourcesthrough a discrete input 200. A second and third redundant serial port202 and 204 may be respectively coupled to line drivers 206, 208,dehydrator 210, 212, device control 214, 216 and low noise amplifier218, 220. A graphical user interface 240 may be used to monitor thevarious conditions of the various devices in the RF chain. The functionof these devices will be further described below. In addition, a testloop translator 242 may also be coupled to one of the serial ports 202,204. The test loop translator 242 may provide an input and outputcarried out by the waveguide and coaxial switches.

The configuration of the primary site 40B may be identical to that ofthe primary site 14A. The diverse sites may also be configured in asimilar manner and have the same inputs 152 through 172. In this case,router 150 is divided up into two routers 250 and 252. A subreflectortracker SRT input 254 and 256 may be provided at each router so that thesubreflector tracking may be performed. An antenna-programmablecontroller (APC) 260 and 262 may be coupled to each serial port which iscoupled to each router 250, 252. In addition, an antenna environmentalsystem (AES) controller 264, 266 may also be coupled to the serial portfor input to the router 250, 252. The remaining elements of the diversesite are identical to those above in the primary site. The diverse site14B may be exactly identical to that of diverse site 42B and the otherdiverse sites in the system.

Referring now to FIG. 4, a method of operating the overall communicationsystem is set forth. In step 300, signals such as television signals arereceived. Of course, various types of signals, including radio or datasignals, may be used. As mentioned above, the television signals may bereceived from various collection points and transmitted to the regionalfacilities. The television signals may be received in many waysincluding over-the-air terrestrial-based or through optical fibers. Thatis, in step 302 the television signals may be communicated to theregional uplink facility. In step 304, the television signals may beuplinked to the satellite. In step 306, the television signals may bebroadcast to various users from the satellites using various types oftransmission methods including spot beams. In step 308, the controlstatus of the regional site 16 may be monitored or controlled at theregional site 16. In step 310, the signals broadcast to the varioususers may also be downlinked at the central facility. The centralfacility may monitor the quality of the signals. In step 312, theregional site 16 itself may be monitored through the graphical userinterface as described above. The same graphical user interfacesprovided at the regional facilities, may be provided at the centralfacility so that various systems may be monitored. It should be notedthat the monitoring of the regional site 16 and the controls therein,may be performed over a terrestrial communication line as describedabove. The communication line may be a dedicated communication line oran internet-type network communication line.

In step 314, the regional site 16 may be controlled using theterrestrial communication line described above. The changing of varioussettings for various RF controls may be set forth and monitored.

In step 316, the control signals are terrestrially communicated to theregional site 16. In step 318, if the terrestrial communication has beeninterrupted, regional control may be the only source of control for theregional facilities in step 320. In step 318, if terrestrialcommunication has not been interrupted, local regional control orcentral control may be performed in step 322. After steps 322 and 320,the system returns back to step 300.

Referring now to FIGS. 5A and 5B, a schematic of a primary site 40 ordiverse site 42 is illustrated. It should be also noted that the centralsite 14 may also be configured in a similar manner.

Each primary site 40 and diverse site 42 includes an indoor portion 400and an outdoor portion 402. The outdoor portion includes a limitedmotion antenna assembly 404.

The indoor portion 400 may receive various channels of televisionsignals. In the present embodiment, four groups of channels A-E, F-J,K-O and P-T are ultimately input to the switch 416. Channel inputs Athrough E may use 950-1,200 Megahertz. Each channel includes a firstmodulator 410 and a second modulator 412. The modulators 410 and 412 areredundant modulators which are controlled by the modulator switch 414.That is, the modulator switch 414 is coupled to redundant modulators 410and 412 and chooses between one or the other switch. The modulatorswitch 414 may be controlled by the control configuration describedabove in FIG. 3. The modulators 410, 412 receive the digital basebandsignals and converts them to a second frequency band such as the L-band.Also, the modulators 410, 412 are used to place the signals into thedesired modulation scheme. As is shown, several groupings of channelsmay be provided. The outputs of each of the modulator switches 414 areprovided to an L-band switch 416. The L-band switch 416 receives thevarious inputs from the modulator switches 414.

Secondary or additional inputs such as engineering inputs ENG1 and ENG2may be used to modulate various signals or provide a set of secondary orback-up modulators or modulator switches if both modulators in one ofthe redundant channels above fail. Also, if one of the modulatorswitches 414 fails, both engineering chains ENG1 and ENG2 are available.The outputs of the additional inputs may be routed to various outputs asa back-up.

The L-band switch 416 may also provide a throughput for basebandmonitoring. This is illustrated as output 12B within the L-band switch.Various engineering inputs may also be switched to various outputsthrough the controller as described above in FIG. 3. For example, shouldthe first channel 1 input chain fail, engineering chain 1 may beswitched to provide an output through the L-band switch. A plurality ofjack fields 418 may also be provided. Jack fields 418 allow the abilityto jack in or connect various inputs including another input or thererouting of various inputs. It should also be noted that each pair ofmodulators for each channel may have a center frequency that is spacedapart by a pre-determined amount. In the present example, the modulatorsare spaced apart by a center frequency of 40 megahertz. The output ofthe L-band switches are grouped together at a summer 412. Another jackfield 424 may be provided so that the signal may be manually monitored.A coupler 430 receives the summed signals from the summing block 420 andprovides them to redundant line drivers 432, 434. A switch 436 selectsone of the outputs of the line drivers 432, 434 to be provided to anoutput 438 of an indoor portion. The output of each of the switches maybe routed to a monitor switch 440. The switch 440, as will be describedlater, provides signals to a spectrum analyzer 442. That is, in theprocess of broadcasting, various signals may be routed to the spectrumanalyzer.

A communication line or plurality of communication lines 444 may be usedto couple the indoor portion 400 and the outdoor portion 402. The L-bandsignals are transmitted through the communication lines 444.

The outdoor portion 402 may be included within a housing 450 of theantenna 404. The outdoor portion 402 includes a splitter 460 that splitsthe signals received from the indoor portion 400 through thecommunication line 444 and provides them to a first block upconverter462 and a second block upconverter 464. Block upconverters 462, 464 havean output provided to a switch 466 which routes the output to a test andmonitor panel 470 or to an output 472. Sample points 474 may be used tosample the output of the switches. Thus, it should be noted that oneoutput of one of the block upconverters 462, 464 is provided to thevariable attenuator. The attenuated signals from the variable attenuatorare used for matching signal levels output from the block upconverter. Asplitter 476 splits the signals and provides them to high poweramplifiers 480, 482. Each high power amplifier may include a monitoringpoint and adjustment point 484, 486 as will be described below. Theoutputs of the high power amplifiers 480, 482 are provided to a variablephase combined amplifier 490. The variable phase combined amplifier 490includes a first output 492 that is provided to a test and monitor panel470. It is desirable for the output 492 of the variable phase combinedamplifier 490 to be zero or nearly zero at the first output. Thevariable phase combined amplifier 492 combines the outputs of the highpower amplifier 480, 482 to generate a high-power output. Should one ofthe high-power amplifiers 480, 482 fail, the output of the variablephase combined amplifier reduces to the output of the working high-poweramplifier. This happens relatively quickly and thus the on-the-airsignal does not become interrupted.

The test and monitor panel 470 is used to monitor the output of thevariable phase combined amplifier 490. A laptop computer or the like maybe carried to the antenna and coupled to the test and monitor panel. AnEthernet connection may also be provided to test and monitor panel. Anadjustment may be made on one or both of the high-power amplifiers sothat the phase is adjusted so that both the outputs of the high-poweramplifiers 480, 482 are in phase.

The output of the variable phase-combined amplifier 490 may be providedto a block downconverter 500. The block downconverter 500 providesoutput back to the indoor portion 400 and eventually back to thespectrum analyzer 442 for monitoring. The first four circuits forvarious groups of channels are identical up to this portion.

The first two groups of outputs from the first two variablephase-combined amplifiers 490 are combined at a diplexer 502. Thediplexer 502 provides the signal to the left-hand circularly polarizedtransmit interface 510 of the antenna 404. A sample may also be taken todetect the power output at power detector 504. A switch 506 may controlthe output to the transmit interface 510 from the diplexer 502. Thesecond two groups of circuitry from the splitter 460 through thevariable phase combined amplifiers 490 are identical. In addition, thediplexer 512 provides a right-hand circularly polarized output through aswitch 514 to the second transmit interface 510.

A power motor calibration unit 520 may also be provided. The powerdetectors 504 may be provided to indoor power meters 628 describedbelow.

A tracking interface 524 coupled to the antenna receives left-hand andright-hand circularly polarized signals that are provided to a switch526. The switch 526 has an output that is passed through a transmitrejection filter 528 to reject the transmitted signal from the receivesignal. An amplifier 530 amplifies the signal and a monopulse plate 532receives the signal. A pair of block downconverters 534, 536 downconvertthe divided signal to a lower frequency such as L-band. It should benoted that the signals received at the tracking interface are from abeacon. The outputs of the block downconverter 534, 536 are provided toa pair of beacon receivers 538, 540 through communication lines 444. Thebeacon receivers 538 and 540 are disposed within the indoor portion. Thebeacon receivers 538, 540 may each be coupled to an antenna control unit542. It should be noted that the beacon receivers 538, 540 are seriallyconnected to a controller or server of the system. Should one of theblock downconverters or one of the beacon receivers fail, one serialinput to the controller may be provided. The beacon receivers 538, 540are also coupled to the antenna control unit 542. The antenna controlunit 542 provides an alternate to the serial interface should the serialinterface fail. The antenna control unit 542 may, for example, becoupled through an Ethernet-type connection. As will be mentioned below,the amount of power to be used in uplinking signals may be determinedusing the beacon receivers. As will be further described below, deicingcontrol 544 may be provided in the indoor portion while the antennadeicing system 546 is provided at the antenna. Deicing may be providedusing hot air techniques.

An antenna interface 550 is provided that receives left-hand andright-hand circularly polarized signals. The left-hand and right-handcircularly polarized signals are provided to switches 552 and 554,respectively. It should be noted that for redundancy three amplifiers556, 558 and 560 are provided. Output switches 562 and 564 are alsoprovided. Sampling points 566 and 568 may be provided prior to theswitches 552 and 554. Also, the output of switches 562 and 564 may becoupled to a bulkhead monitor connection 570. The output of switches 562is provided to a first splitter 574 and a second splitter 576. The splitsignal is provided to a first block downconverter 580, a second blockdownconverter 582, and the output of the second splitter 576 is providedto a third block downconverter 584 and a fourth block downconverter 586.The output of the block downconverters 580-586 is provided to a couplerwhich in turn may couple the signals to the switch and ultimately to thespectrum analyzer 542.

The antenna control unit 542 may be coupled to the drive cabinet 590which in turn is coupled to an isolation transformer 592.

Various other equipment may also be included in the indoor portion suchas dehydrators 600, 602 that are provided to a manifold and monitor 604.A pressure gauge output 606 is provided to the dry air interfaces. Anisolated ground bar 610 may be provided within the outdoor portion. Theindoor portion may also include a block upconverter in variable powercombined amplifier control 612.

A monitor and control rack 616 may be used to house the variousequipment. The rack may be shared for multiple systems. The rack 616 mayinclude serial, discrete and Ethernet interfaces for use in multiplesystems.

A pair of GPS receivers 618, 620 with redundant antennas 52A, 52B mayalso be provided. The GPS receivers 618, 620 provide outputs to switches622. The GPS receivers 618, 620 may be used to provide a precise timemonitor so that precise timing may be provided for the primary site anda reference for switching which will be later described below for thediversity site as provided.

Power meters 628 may also be provided to monitor the pre-transmit powerof the system from power detectors 504. Spare Ethernet connections 620and spare cable 622 may also be provided.

The antenna may also include various centers such as a feed temperaturestatus sensor 630, carbon monoxide sensor 632, a hub temperature status634 and a hub door switch 636. Each of these parameters may be providedto the servers for display on a graphic user interface.

Various test points along the circuiting are used to provide the systemoperators with an assessment of the signals. If one component is notworking, a back-up component may be used. Also, the signals may bemonitored at various locations so that the precise location of thefailing or failed component may be determined.

Referring now to FIG. 6, an enlarged view of the limited motion antenna404 is illustrated. Antenna 404 includes housing 450 that houses much ofthe circuitry in the outdoor portion of FIG. 5. The antenna may bemounted on a concrete stand 650 that includes a stairway 652 so that thehousing 450 may be reached. Transmit interface 510, tracking interface524 and receive interface 550 are shown.

Referring now to FIG. 7, a high level flowchart executed by thecontrollers or servers within the system illustrates the flow ofswitching between the primary site and the diverse sites. Several of thesteps illustrated by a double rectangle method are described in detailin other figures. In step 700, the diverse switching method is started.In step 702, a manual or automatic switch position is determined. Instep 704, the diverse switch is not in an automatic setting. Step 702 isagain executed. In step 704, the diverse switch is in automatic. Step706 determines if the diverse site is not on the air. If the diversesite is not on the air, the equipment status of the diverse site ischecked. This will be described below in a further flowchart. If thestatus returned in step 708 is good in step 710, the system continues tostep 712 which determines if a trigger point from the diverse site isreached. Trigger point 1 initiates initialization of the diverse sitewhich will be described below. In step 714, if the method determinesthat continuation to the diverse site is warranted, step 716 isperformed. In step 716, if the primary site trigger point 2 has beenreached, step 718 is performed. In step 718, if the trigger point 2 hasbeen reached, step 720 is performed which initiates the primary todiverse switch site. This will be further described below. After step714 and 718, if the answer to either of the questions is no, step 702 isagain executed. Also, after step 720 and the primary site has beenswitched to the diverse site, step 702 is again executed.

Referring back to step 706, if the diverse site is on the air, step 724is performed in which the primary site clear sky time duration isdetermined. After the sky has been cleared for a certain amount of time,the system may again switch to the primary site. After step 724, step726 determines whether or not to continue to the primary site based uponthe clear sky time duration. If a continuation to the primary site isperformed, a switch to the normal path is performed in step 728. Afterstep 728, 702 is executed.

If a continuation to the primary site is not warranted in step 726, step730 is performed in which a diverse site equipment status is performed.This will be described below. In step 732, if the status if good, step734 is performed in which the primary site is initialized if triggerpoint 1 is reached. In step 736, if continuation to the primary site iswarranted, step 738 determines whether the diverse site trigger point 2has been reached. This will be described further below. In step 740, ifa continuation to the primary site is determined by checking the diversesite trigger point, step 42 initiates a switch from the diverse site tothe primary site. After step 742, step 702 is again performed.

Referring back to step 710 and step 732, if the status of the primarysite in step 710 or the status of the diverse site is not good in step732, steps 744 and 746 are respectively performed. Steps 744 and 746will be further described below.

After steps 744 and 746, step 702 is again performed.

It should be noted that the various trigger points and the steps to theprocess may be displayed on a graphical user interface shown in FIG. 3.

Referring now to FIGS. 8A and 8B, the process for checking the equipmentstatus of the primary site in step 708 of FIG. 7 and checking theequipment status of the diverse site in step 730 of FIG. 7 are nearlyidentical. Therefore, each of the identical steps is labeled in FIG. 8Bwith a prime. The steps are identical except for the reference to eitherthe primary site or the diverse site depending on the original step.Therefore, FIG. 8A will be discussed and the changes to FIG. 8B will behighlighted.

In step 800, the primary site equipment status is displayed as red orother indicator on the Graphical User Interface. If there is nocommunication fault at the primary site, step 804 is performed in whichone or both of the traveling wave tubes are determined if they areready. If the traveling wave tubes are ready, step 806 is performed inwhich it is determined if the primary site uplink power control isactive. If the uplink power control is active, the system returns backto step 710 of FIG. 7 in step 808. If a communication fault is presentat the primary site or one or both of the traveling wave tubes is notready in step 806 or the primary site does not have the uplink powercontrol ready, step 810 generates a message of the primary site failureand sets the diverse switch to manual in step 812. Step 818 sets theprimary site display to red or other indicator and returns a NO statusin step 816 so that step 744 of FIG. 7 is performed.

Referring now to FIG. 8B, each of the same process steps of FIG. 8A isperformed except with reference to the diverse site. If the diverse siteis ready in step 808 prime, the status is good and the system continuesto step 734 of FIG. 7. If the diverse site is not ready, the systemreturns to step 732 in which the status would not be good and thus step746 is performed thereafter. In step 814 prime, the diverse sitegraphical user interface is displayed to red.

Referring now to FIGS. 9A and 9B, steps 744 and 746 of FIG. 7 areillustrated in further detail. In step 840, the diverseradiate/terminate switch position is determined. In step 842, if theswitch is not in radiate position, step 844 is performed in which acommand to change the diverse radiate/terminate switch position toradiate is performed. If the switch is not in the radiate position instep 846, step 848 generates a message that the primary to diverseswitch failure is performed. In step 850, the primary site graphicaluser interface may be changed to a different color such as red toindicate a failure. The system returns in step 852. Referring back tosteps 842 and 846, if the switch is placed in radiate, step 854 un-mutesthe diverse block upconverter or removes the traveling wave tube inhibitsignal. In step 856, a primary site timer delay (P2D) is performed. Ifthe delay is achieved in step 858, the system continues to step 860. Ifthe delay is not achieved, step 856 is continually performed until thedelay has been achieved. In step 860, the primary block upconverter ismuted or the traveling wave tube is set to inhibit. In step 862, thediverse site graphical user interface is changed to an indicator such asgreen to indicate the diverse site is operating.

Referring now to FIG. 9B, similar steps to those shown in 9A areillustrated except that the diverse to primary switchover is performed.The process in FIG. 9B returns in step 842 prime to step 746 of FIG. 7.

Referring now to FIGS. 10A and 10B, step 712 and 734 of FIG. 7 areperformed. Again, these figures are complimentary. In step 712 of FIG.7, the steps necessary to prepare the diverse site during a first fadeevent is determined. In step 880, the primary site fade level isdetermined. The primary site fade level may be determined using receivedbeacons as will be further described below. In step 880, the primarysite variable phase combined amplifier status is determined. If thevariable phase combined amplifiers are not combining the traveling wavetubes (HPAs 480, 482 of FIG. 5) in step 844, step 886 is performed inwhich it is determined whether the fade of the primary site minus threedecibels, the answer is no, the system returns to step 890. In step 884,if the variable phase combined amplifiers are combining the travelingwave tubes outputs, step 888 is performed. If the fade is not greaterthan a threshold such as TP1, step 890 is again performed and the systemis returned. In steps 886 and 888, if the system is greater than testpoint 1 minus 3 decibels or is greater than test point 1 in step 888,step 892 the primary switch from radiate determining is performed aswill be further described below in FIG. 11.

After step 892, the system returns to step 894 with a YES status to step714.

Referring now to FIG. 10B, the identical steps are performed except withrespect to primary site initialization. Steps 886 prime and 881 primeuse a fade threshold TD1 of the diverse site for its variable. Thevariable TD1 and TP1 may be equivalent.

Referring now to FIGS. 11A and 11B, steps 892 and 892 prime of FIGS. 10Aand 10B are illustrated in further detail. Yellow may be used as adisplay for a “hot standby” where the radiate/terminate switch(controlling its block upconverter for example) is in the radiateposition with the signal still muted at the diverse site. Red may beused as a failure. In step 900, the diverse radiate switch position isread. In step 902, if the switch is not in radiate position, a commandis generated to change the switch to the radiate position in step 904.After step 904, step 906 is performed. Steps 902 and 906 determine ifthe switch is in radiate position. In steps 902 and 906 if the switch isin radiate position, step 908 is performed in which the diverse sitegraphical user interface is displayed differently such as in “yellow.”In step 910 the system returns a YES status back to step 712 in step894.

Referring back to step 906, if the switch is not in radiate position instep 906, step 912 generates a message of diverse site failure and step914 sets the diverse switch to manual. Step 916 generates a graphicaluser interface color such as red to indicate a problem with the diversesite. In step 918, the system returns a NO to step 894.

Referring now to FIG. 11B, the identical process is used for determiningwhether the primary switch is in radiate or terminate. Therefore, thesecommands will not be further described below.

It should be noted that the above first fade function is where a “hot”standby mode is entered. If in the loop the system returns back to aclear sky, the system will return back to the primary function. Ifconditions worsen, a second threshold level converts the system intotransmitting to the other site. That is, if the primary site istransmitting, a diverse site is used. If the diverse site istransmitting, the primary site is used.

Referring now to FIG. 12A, step 716 of FIG. 7 is illustrated in furtherdetail. In step 950, the primary site fade level is determined. Asmentioned above, the fade level may be determined based upon thereceived beacon signals. In step 952, the primary sites variable phasecombined amplifiers status is determined. If the variable phase combinedamplifiers are combining the traveling wave tubes (HPA) outputs in step954, step 956 is performed. In step 956, if the primary fade level isnot greater than a second threshold (TP2), step 958 is performed. If theprimary fade level is less than the first threshold (TP1), step 950 isagain executed. After step 958, if the primary fade level is less thantest point 1 (TP1), step 960 is performed. Step 950 will be furtherdescribed below. After step 960, the system returns a NO back to step716 in step 962.

Referring back to step 956, if the primary fade level is greater thanthe second threshold TP2, step 964 is performed. Referring back to step954, if the variable phase combined amplifiers are not combining thetraveling wave tube outputs, step 966 is performed. If the primary fadeis greater than a second threshold minus three decibels or some othervalue, step 964 is performed. In step 966, the diverse site variablephase combined amplifier status is determined. In step 968, if thevariable phase combined amplifiers are combining the traveling wave tubeoutputs, step 970 is performed in which a diverse fade it is determinedwhether the diverse fade is less than the diverse test second (TD2)threshold. If the diverse fade is not less than the diverse secondthreshold (TD2), step 962 returns a NO status. Referring back to step970, if a diverse fade is less than the second diverse threshold, step972 is performed.

Referring back to step 968, if the variable phase combined amplifier isnot combining the traveling wave tube (high power amplifier outputs),step 974 is performed in which it is determined whether the diverse fadeis less than the second diverse threshold minus three decibels. If thediverse fade is not less than the diverse threshold minus threedecibels, step 962 is again performed. In step 974, if the diverse fadeis less than the second diverse threshold minus three decibels, step 972is performed. Step 972 performs a diverse site equipment status that wasdescribed above in steps 708 and 730 and in FIGS. 8A and 8B.

If the status is good in step 976, a return of YES is performed in step978. If the status is not good in step 976, step 962 returns a NO statusin 716.

Referring back to step 966, if the primary fade is not greater than thesecond primary threshold minus three decibels, step 980 is performed. Instep 980, if the primary fade is not less than the first primarythreshold minus three decibels, step 950 is performed. This performs noswitchover. In step 980, if the primary fade is less than the firstprimary threshold minus three decibels, step 982 is performed in which aprimary clear sky normalized diverse site function is performed. Thisstep will be further described below. After step 982, step 962 returns aNO condition.

Referring now to FIG. 12B, the identical process with respect to thediverse site trigger point 2 (TP2) is performed. Thus, the entireprocess is exactly the same except that the thresholds have been changedfrom the primary thresholds to the diverse thresholds in steps 958′,966′ and 960′. The thresholds have been changed in steps 970′ and 974′from the diverse thresholds to the primary thresholds in steps 970′ and974′. Also, steps 960 and 982 do not have a corollary in FIG. 12B.

Referring now to FIG. 13A, steps 960 and 982 are identical steps fromFIG. 12 that normalize the radiate/terminate switch at the diverse siteafter a set amount of time of a primary site clear sky condition. It isdesirable to broadcast using the primary site when conditions aresuitable. In step 1000, if a clear sky counter has not been started,step 1002 starts a clear sky counter. The system then returns to step1004.

Referring back to step 1000, if the clear sky counter has been started,step 1006 reads the clear sky counter. In step 1008, if the counter isnot equal to 30 minutes, the system returns to step 1004. If the counteris equal to 30 minutes in step 1008, step 1010 commands the diverse siteradiate/terminate switch to terminate. In step 1012, if the terminateswitch is not in terminate, the diverse switch is set to manual. In step1014, a message of switch failure is generated in step 1016 and diversesite graphical user interface may be displayed in a red color toindicate a failure. In step 1020, a counter is stopped.

Referring back to step 1012, if the switch is in a terminate condition,the diverse site graphical user interface (GUI) is displayed in a lightblue or other color indicator in step 1022. In step 1020, the counter isstopped to indicate the system has now been changed over to the primarysite.

Referring now to FIGS. 14A and 14B, steps 720 and 742 of FIG. 7 areillustrated in further details. In step 1040, the block upconverter maybe used to initiate or discontinue transmission. Also, the travelingwave tube inhibit function may also be used to inhibit or enabletransmission. In step 1040, the diverse block upconverter is un-muted.In step 1042, the diverse timer (P2D) delay is read. If the delay hasnot been achieved in step 1044, step 1042 is again performed. If thedelay has been achieved in step 1044, step 1046 mutes the primary blockupconverter or sets the traveling wave tube to inhibit. In step 1048,the diverse site graphical user interface may be changed to a differentcolor such as green to indicate it is transmitting. In step 1050, theprimary site graphical user interface is set to a yellow or differentcolor to indicate a stand-by mode. In step 1052, the system returns tostep 720.

Referring now to FIG. 14B, steps 1040 prime through 1052 prime areidentical except with respect to the primary site rather than thediverse site. Therefore, these steps will not be further describedbelow.

Referring now to FIG. 15, step 724 of FIG. 7 is described in furtherdetail. Once the primary site enters into a clear sky condition, thisfunction will time the switch over to the primary path either by a timeror manually entered set time clock. If a rain fade or equipment failureoccurs during this routine, the function is not performed.

In step 1100, if the timer is selected, step 1102 sets the timer to avalue such as 60 minutes. In step 1104, if the time has expired, step1106 returns a YES function, yes to step 724. In step 1104, if the timehas not expired, the primary site fade level is determined in step 1106.In step 1106, the primary site fade level is determined. After step1106, step 1108 reads the primary variable phase combined amplifierstatus. In step 1110, if the variable phase combined amplifier iscombining the traveling wave tube outputs, step 1112 determines whetherthe primary fade is less than the first primary threshold. If theprimary fade is less than the first primary threshold (TP1), step 1114is performed. Step 1114 performs a primary site equipment status. Instep 1114, if the status is good in step 1116, the diverse site fadelevel is determined in step 1118. In step 1120, the primary variablephase combined amplifier status is determined.

In step 1122, if the variable phase combined amplifiers are combiningwith the traveling wave tubes in step 1112, step 1124 is performed inwhich the fade level is compared to the diverse site threshold. If thediverse site fade is less than the first diverse site threshold (TD1),the system returns to step 1106. In step 1122, if the variable phasecombined amplifier is not combining with the traveling wave tube, step1126 is performed in which it is determined whether the diverse fade isless than the first diverse threshold minus three decibels. If it is instep 1126, step 1128 is performed in which the diverse site equipmentstatus is determined. A diverse site equipment status is also determinedif the diverse fade is less than the first diverse threshold in step1124. In step 1126, if the answer is NO, step 1106 is performed.

Referring back to step 1128, if the diverse site equipment status isperformed, step 1130 is performed in which it is determined whether thestatus is good. If the status is not good, the system returns a YES insteps 1106. If the status is good, step 1100 is again performed.

Referring back to step 1100, if the timer is not selected, step 1132 isperformed. In step 1132, the clock is set to a default time such as time0100 and step 1134 is determined. In step 1134, if the clock does equalthe selected time, step 1106 returns a YES.

Referring back to step 1110, if the variable phase combined amplifiersare not combining with the traveling wave tube, step 1136 is performedin which the primary fade is compared to the first primary threshold(TP1) minus three decibels. If the primary fade is less than the firstthreshold minus three decibels, step 1114 is performed. In step 1136, ifthe primary fade is less than the first primary threshold minus threedecibels, step 1138 returns a NO in step 724.

Referring now to FIG. 16, an initiate switch to normal path function isperformed that corresponds to step 728 of FIG. 7. This function placesthe primary site back on the air. After the switch occurs, a primarysite is placed into on-the-air and the graphic user interface may beplaced to green.

The diverse site may be placed into a warm standby mode in which thestatus may be changed to a light blue and the radiate/terminate switchplaced into terminate at the diverse site. In step 1150, the diverse toprimary switching is performed. This corresponds to step 742 and wasdescribed in FIG. 14B above. In step 1152, the diverse radiate/terminateswitch is commanded to terminate. In step 1154, if the switch is interminate, step 1156 sets the diverse site graphical user interface tolight blue or provides another indicator. The system returns in step1158. In step 1154, if the switch is not in terminate, step 1160 setsthe diverse switch to manual. In step 1162, a message of switch failureis generated. In step 1164, the diverse site graphical user interface ischanged to display a red or other indication of a site failure.

Referring now to FIG. 17, a summary of the method of changing between aprimary site and a diverse site is set forth. Generally, the followingmethod is used to project into the future a switching time taking intoconsideration various factors. A future switching time is determinedboth for the primary site and the diverse site so that a user has aslight gap between receiving the signals from the primary site andsignals received from the diverse site.

In step 1200, uplinking is performed using the primary site. In step1202, a changeover trigger is determined. The changeover trigger isdescribed above as an increase in rain fade, an emergency condition, amaintenance condition or the like.

In step 1204, a time to communicate with a diverse site is determined.The time to communicate with a diverse site includes many factorsincluding the type of connection, the exclusivity of the connection, thespeed at which the information travels, and the distance between theprimary site and the diverse site. The distance may be a significantfactor since a diverse site may be separated by a primary site by tensof miles such as 50 miles. As mentioned above, the signals may becommunicated in a video over internet protocol format. This time may bemeasured experimentally. It may be determined at various timesthroughout the day or determined right before a changeover is required.

In step 1206, the time to perform the switchover routine is alsodetermined. This is the time that it takes to process the changeover andmay thus be referred to as a switchover processing time. As wasmentioned above, the block upconverters may be used to control theswitchover. The block upconverter may be controlled by the controllerwhich takes a finite amount of time to command and to switch-on orpower-up and switch-off or power-down the device.

In step 1208, an amount of time gap to generate at a receiving device isdetermined. The gap may be calculated at the primary site. The time gapis determined so that at the receiving device signals uplinked from theprimary site are received followed by an empty space, or gap, wherethereafter the signals uplinked from the diversity site begin. This maybe also experimentally determined. The time gap may vary but should besmall enough to be compensated in an error control module as describedbelow.

In step 1210, a precise time at the primary and diverse site isdetermined using various methods that may include receiving a globalpositioning signal having the time therein.

In step 1212, the future time for switching the primary site to OFF isdetermined. That is, the time for switching the primary site to OFF isprojected slightly into the future. The future time for switching theprimary site to OFF may take into consideration the various parametersset forth above in steps 1206, 1208 and 1210. Namely, the time fordetermining the site to switch up may take into consideration the timesdetermined in steps 1204 through 1208. Also, in step 1214, the futuretime for the diversity site to switch-ON or broadcast is alsodetermined. Both of the times are based upon the parameters such as thetime to communicate with the diverse site, the time to perform theswitchover routine and the time to generate a gap between the devices.In step 1216, the primary site stops broadcasting based upon the futuretime set forth above and the diverse site begins broadcasting in step1218.

In step 1220, the primary signals, gap and diverse site signals arereceived in that order at the receiving device. In step 1222, errorconcealment is performed at the receive device before the signals aredisplayed on the television in step 1224. Any residual time gap in thereceived signals is removed.

Referring now to FIG. 18, the IRD 74 and antenna 72 illustrated in FIG.1 is set forth in further detail. The IRD 74 may include an errorconcealment module 1240 among its other known functions such as tuningin tuner 1242, demodulating in demodulator 1244 and decoding in aforward error correction decoder 1246. Controller 1248 may contain theerror concealment module 1240. The error concealment module 1240performs many functions including removing slight gaps ordiscontinuities in the signal so that they are not readily observable bythe viewer in an output signal 1249.

Referring now to FIG. 19A, an integrated receiver decoder (IRD) 74 isillustrated receiving a primary site signal 1250, followed by a time gap1252, followed by the diverse site signal 1254 in accordance with themethod set forth in FIG. 17.

Referring now to FIG. 19B, IRD 74 is shown transmitting primary sitesignal 1255 and diverse site signal 1251. The IRD 74 may modify thesignals to remove any gap between them so that the television 76 has noobservable gap therebetween. It should be noted that various techniquesfor error concealment, such as digitally manipulating the signals andthe user of buffers, is known in current generation DirecTV integratedreceiver decoders. This error concealment can be used to allow a gapbetween the signals. By providing a gap, an overlap in the signals isavoided. An overlap in the signals may cause errors in the integratedreceiving device 74.

Referring now to FIG. 20, a method for changing the uplink power is setforth. It should be noted that the uplink power applies to the primarysite, the diverse site or the central site 14. In step 1270, a clear skyuplink power is established. This is a baseline and a delta from thebaseline will be determined below. In step 1272, a first beacon signalis received and converted to a first beam power signal. In step 1274, asecond beacon signal is received and converted to a second beacon powersignal. The beacon power signals in step 1272 and 1274 are receivedusing the antenna 404 and the associated circuitry set forth above,including the beacon receiver and the block downconverter illustrated inFIG. 5. In step 1276, the first beacon power signal and the secondbeacon power signal are compared. The comparison compares the firstbeacon power signal and the second power beacon signal. In step 1278,the strongest powered beacon signal is selected to form a selectedsignal. In step 1280, the amount of fade in terms of power isdetermined. In step 1282, a fade threshold is established. In step 1284,the uplink power is determined as a delta (A) of the clear sky power.That is, based upon the threshold and the amount of fade, a new uplinkpower may be determined. The beacon power signal may be broadcast tomultiple pieces of equipment. Each piece of equipment (such as thoseshown in FIG. 5) may then use the beacon information for various controlmethods. Amplifiers and block upconverters (BUC) are examples ofsuitable equipment to receive the beacon power signals. A suitablebroadcast method is through the Ethernet connection. Each device such asthe amplifier and BUC then determines a fade and an adjustment for fade.The amplifier and block upconverter act as a controller in this respect.

Once the new uplink power is determined, the uplink speed is determinedin step 1286. If the uplink speed is greater than a pre-determinedspeed, the uplink power is limited in step 1288. The uplink speed limitshow quickly the uplink power is ramp. It operates as a second layer ofprotection so that the high power amplifiers prevent ramping power soquickly that a large phase shift is introduced in the uplink that maycause the receivers on the ground to momentarily loose lock. Typicalvalues of uplink speed are one to three decibels per second. After step1288 and after step 1286 if the uplink speed is greater than the uplinkspeed, the uplink forward power limit is compared to the uplink powereddetermined in step 1284 or 1288 in step 1290. If the uplink power isover the forward limit, then the power is limited in step 1292 to themaximum power that a block upconverter should be commanded to. If theuplink power is not over the forward limit, and after step 1282 theantenna is broadcast with the calculated uplink power in step 1294.

Referring now to FIG. 21, a plot of the uplink power versus fade isillustrated. The lower horizontal line corresponds to the clear skypower. The fade thresholds T is also illustrated. The second horizontalline 1302 illustrates the forward power limit.

It should be noted that the beacon signals in step 1272 and 1274 arelocked on to the same downlink beacon signal. The uplink powercompensation may be based on a unit-less constant, K, the fade, thetransmit and receive signal frequency and a fade threshold T. The fadeis a calculated value within the server or controller. The K value, thetransmit and receive signal frequency values and the threshold valuesmay all be user generated. These values may be experimentally determinedbased in part on the capabilities of the particular transmittingcapabilities. The uplink power control (UPC) is best defined as:UPC=K(FADE−THRESHOLD)(F _(Tx) /F _(Rx))²

Referring now to FIG. 22, a method of operating the system isillustrated. The system may be also understood with reference to FIG. 5.

In step 1320, a tracking interface is selected. The tracking interfaceis illustrated as 524 and is coupled to the antenna. In step 1322, abeacon signal is received. This may include error checking, amplifyingand passing the signal through a monopulse plate 532. In step 1324, thebeacon signal is divided into a first beacon signal and a second beaconsignal at the monopulse plate 532. The first beacon signal and thesecond beacon signal are passed to block downconverters 534, 536. Instep 1326, the first beacon signal is block downconverted and in step1328, the second beacon signal is block downconverted. The signals arethen communicated in step 1330 to the indoor unit and to respectivebeacon receivers 538 and 540 of FIG. 5 through a communication line 444.In step 1332, the beacon signals are serially connected to a controllerto determine uplink power. In step 1334, the serial connection ischecked to determine whether or not the serial connection has failed. Ifthe serial connection has not failed, the uplink power is determined instep 1336 and the new uplink power is used to broadcast the signal instep 1338.

If the serial connection has failed in step 1334, the antenna controlunit may be coupled to each of the beacon receivers 538 and 540. Theantenna control unit 542 has an Ethernet connection to the controller.The beacon signals are communicated through the Ethernet connectionthrough the antenna control unit 542 in step 1340. The controller thendetermines the uplink power in step 1336 and broadcasts with that uplinkpower in step 1338.

Those skilled in the art can now appreciate from the foregoingdescription that the broad teachings of the disclosure can beimplemented in a variety of forms. Therefore, while this disclosureincludes particular examples, the true scope of the disclosure shouldnot be so limited since other modifications will become apparent to theskilled practitioner upon a study of the drawings, the specification andthe following claims.

1. A system comprising: a satellite; a regional site uplinking regionaluplink signals to the satellite and communicating condition signals to acentral site through a terrestrial communication link; the satellitegenerating regional downlink signals from the regional uplink signals;and said central site receiving the regional downlink signals from thesatellite and terrestrially receiving the condition signals andcommunicating control signals for the regional site through theterrestrial communication link.
 2. A system as recited in claim 1wherein the regional uplink signals comprise a Ka band uplink signal. 3.A system as recited in claim 1 wherein the regional site controls theregional site upon interruption of the terrestrial communication link.4. A system as recited in claim 1 wherein the terrestrial communicationlink is a dedicated terrestrial communication link.
 5. A system asrecited in claim 1 wherein the regional site comprises a regionalprimary site generating a regional primary uplink signal and a regionaldiverse site generating a regional diverse uplink signal.
 6. A system asrecited in claim 5 wherein the regional primary uplink signal and theregional diverse uplink signal comprises a digital television signal. 7.A system as recited in claim 5 wherein the regional primary uplinksignal and the regional diverse uplink signal comprises ahigh-definition digital television signal.
 8. A system as recited inclaim 5 wherein the regional primary site and the regional diverse siteare geographically separated.
 9. A system as recited in claim 8 whereinthe regional primary site and the regional diverse site aregeographically separated by at least 25 miles.
 10. A system as recitedin claim 8 wherein the regional primary site and the regional diversesite are geographically separated by at least 40 miles.
 11. A system asrecited in claim 8 wherein the central site comprises a central primarysite and a central diverse site.
 12. A system as recited in claim 8wherein the central primary site and the central diverse site aregeographically separated.
 13. A method comprising: uplinking regionaluplink signals to a satellite; communicating condition signals to acentral site through a terrestrial communication link; generatingregional downlink signals at the satellite from the regional uplinksignal; receiving the regional downlink signals at the central site;receiving the condition signals at the central site; generating controlsignals at the central site for the regional site; and communicating thecontrol signals through the terrestrial communication link from thecentral site.
 14. A method as recited in claim 13 wherein uplinkingcomprises uplinking the regional uplink signals from a regional primarysite.
 15. A method as recited in claim 14 wherein uplinking comprisesuplinking the regional uplink signals from a regional diverse site. 16.A method as recited in claim 15 further comprising switching to theregional diverse site from the regional primary site and uplinking theregional uplink signals to the satellite from the regional diverse site.17. A method as recited in claim 16 wherein switching comprisesswitching in response to an error condition in the regional primarysite.
 18. A method as recited in claim 17 further comprising detectingthe error condition at the central site.
 19. A method as recited inclaim 17 further comprising detecting the error condition at theregional site.
 20. A method as recited in claim 16 wherein switchingcomprises switching in response to a manual switch.
 21. A method asrecited in claim 13 further comprising detecting an interruption of theterrestrial communication link and controlling the regional site at theregional site.